Impaired Loans and Allowance for Loan Losses - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Newly identified TDRs	$ 2,000,000
Troubled Debt Restructuring Outstanding	17,700,000	$ 20,000,000
Loans and Leases Receivable, Impaired, Troubled Debt, Interest Income	1,586,000	880,000	$ 1,345,000
Loans and Leases Receivable, Impaired, Interest Income Recognized, Change in Present Value Attributable to Passage of Time	$ 235,000	318,000	456,000
Loan Default Period	90 days
Impaired Financing Receivable, Average Recorded Investment	$ 31,187,000	38,514,000	49,600,000
Nonaccrual loans and loans past due ninety days	18,100,000	17,400,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0	17,000
Provision for Loan, Lease, and Other Losses	2,411,000	2,644,000	(3,486,000)
Allowance for Loan and Lease Losses, Write-offs	$ 1,375,000	3,599,000	2,755,000
Purchased Unimpaired Loans [Member]
Financing Receivable, Modifications [Line Items]
Provision for Loan, Lease, and Other Losses		1,300,000
Allowance for Loan and Lease Losses, Write-offs		1,200,000
Purchased Loans [Member]
Financing Receivable, Modifications [Line Items]
Loan Default Period	90 days
Nonaccrual loans and loans past due ninety days	$ 2,763,000	2,464,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0	196
Financing Receivable, Recorded Investment, Past Due	2,867,000	4,628,000	2,577,000
Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Nonaccrual loans and loans past due ninety days	11,024,000	12,758,000	18,563,000
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Newly identified TDRs	1,200,000
Impaired Financing Receivable, Average Recorded Investment	21,385,000	25,395,000
Provision for Loan, Lease, and Other Losses	(1,145,000)	(2,208,000)	(1,651,000)
Allowance for Loan and Lease Losses, Write-offs	215,000	779,000	$ 1,126,000
Loans [Member] | Bank shares, Inc [Member]
Financing Receivable, Modifications [Line Items]
Assets, Fair Value Adjustment	$ 13,700,000	$ 14,200,000
Fair value adjustment Percent	3.11%	4.43%